in an open letter to the president today, eight big city mayors from new york to los angeles asked for an outright ban on assault weapons. >> it's clear that gun is not for the streets it's not for sports. it's really a gun of war. >> reporter: san francisco mayor ed lee and oakland mayor jean quan agree with the federal assault weapons ban that's already in place in california. the two cities just had their largest gun buy-back event taking 600 firearms off the streets. >> the reality is we can buy back hundreds but if we can't stop the flow into nevada and increasingly now for the internet and other sources, this is where we really need and that's why i think you see the mayors across the country trying to put pressure on the federal government. >> reporter: but will public sentiment last long enough to fight strong lobbying groups line the nra? san jose mayor chuck reed weighed in. >> i think people have a right to not necessarily use assault weapons anytime anywhere they want. and i think within the limits of the constitution, there are things we can do and we should. >> some may s